Integrated circuit devices are formed on semiconductor substrates, or wafers. The wafers are then sawed into microelectronic dies, or semiconductor chips, with each die carrying a respective integrated circuit. Each semiconductor chip is mounted to a package, or carrier, substrate, which is then mounted to a circuit board, or motherboard, before being installed in an electronic system.
The two most common types of electrical connections made from the die to the package substrate are known as wirebonding and “flip-chip” connections. Wirebonding generally involves running a wire from an appropriate contact point on the die to such a point on the package substrate. Flip-chip connections, which for many applications are considered to be superior, involve forming conductors from the integrated circuits on the front side of the die using solder to make connections to the package substrate.
One of the problems associated with the manufacturing of flip-chip connections is that, because solder is used to electrically and mechanically connect the die to the package substrate, the metals used on both the package substrate and the die must be compatible with the particular solder processing that is used. This problem is particularly prevalent when gallium arsenide substrates are being used, as gold is the most common metal that is used to form the conductors on the die. Because gold readily reacts with the tin present in most solders, especially the tin-rich, lead-free solders, the conductors are often destroyed during the multiple heating processes that are required to complete the manufacturing of the packaged devices. This is especially frequent when the gold conductors contact the heated solder.
Accordingly, it is desirable to provide a method for forming a microelectronic assembly having interfaces that allow solder to be used to form connections to package substrates and the like. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.